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Technical Bulletin 8 2006

Equine Wound Management

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Index/contents

Page No. 1. Introduction 4 2. Types of wounds 5 3. Wound healing 9 4. Principles of wound management 12 5. Basic wound management protocol 16 6. Topical medications 17 7. Dressings and Bandaging 19 8. What NOT to use on wounds 24 9. Factors affecting healing 25 10. Other complications and wound management techniques 28 11. Extension messages to owners 34 12. References 35

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Acknowledgements

With grateful thanks to Professor Derek Knottenbelt for permission to use extracts from his text books and for help and advice on the draft. Thanks are also due to Brigitte Clark and Accurate Translations who translated the Bulletin into French and Arabic respectively. Jeremy Hulme kindly did the drawings and diagrams. All photographs are from the SPANA photo library.

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1. Introduction A wound is: a break in the integrity of the skin; an injury to the body which causes a disruption of the normal continuity of the body structures. Treatment of wounds is one of the most common procedures carried out by SPANA personnel; in 2006 SPANA treated over 50,000 equids with wounds. The type of work carried out by working equids in countries where SPANA operates puts them in positions where they frequently sustain wounds. Their general health, poor nutrition levels, overwork and the poor conditions of harnessing and farriery will also increase the likelihood of sustaining wounds. Wounds are detrimental to animal welfare in the short term and, if left untreated or improperly treated, can cause long term suffering. A wounded animal also represents a reduced income for an owner and his/her family since the horse, donkey or mule will not be able to work at its usual strength and may become debilitated and unable to work at all. The treatment and management of wounds is a rapidly evolving specialisation, including within the equine field and there have been considerable advances in our understanding of wound healing mechanisms over the past 10-20 years. The increasing availability of wound dressings in many countries also allows us to modify our wound care protocols. In most cases we no longer have to rely on strong iodine solution dabbed on to a wound, followed by a spray of purple antibiotic. Our understanding of wound healing allows us to provide the correct local environment in which a wound will best heal, as well as identify factors at the outset that may prevent or slow healing. However, it remains a fact that some wounds on equids take a considerable time to heal or do not heal, despite removing the inhibitory factors as far as possible. It is therefore, just as vital that SPANA personnel are active in promoting preventive health to owners, advising on good harnessing, farriery, work practices and housing. With wounds on equids, prevention is definitely better (and cheaper for the owner in the long term) than cure.

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2. Types of wounds Wounds may be classified as the following: Graze/Abrasion/Erosion Usually an irregular shaped wound, often superficial, not extending through the full thickness of the skin. There may be a little capillary bleeding (ooze) and a small amount of serum exudate. Often caused by rubbing against a rough or hard object (eg a road surface). Healing is usually straightforward and rapid with no scarring. The wound needs to be managed to allow this healing and analgesics(pain killers) may be required.

Bruise/Haematoma/Contusion A bruise consists of bleeding and tissue damage within or just under the skin with no skin break. It can, however, occur next to a lacerated wound. It is often caused by blunt trauma. Bruises can be difficult to see in dark skinned equids. If multiple bruises are seen and there is no obvious cause, then the animal’s blood clotting ability should be checked. Treatment is often not required except for certain sites, such as the penis or eyelids, when ice packs or cold hosing may be necessary to reduce swelling. Healing of a bruise is usually straightforward. A haematoma is a swelling due to an accumulation of blood (or serum or plasma) under the skin, caused by blunt trauma. It can be differentiated from the swelling due to an abscess or oedema by pressing a finger on the swelling: an abscess will rarely allow an indentation; oedema will leave an impression on the finger press that remains a few seconds after removing the finger; with a haematoma an indentation can be made by the finger, but this disappears immediately when the finger is removed. Treatment of a haematoma may be by leaving it for the clot to organise or by draining. Healing can take time, especially if there is continued bleeding or abscessation. Scarring is common. A contusion is common and is a severe bruise with skin injury. It is often seen on the head (eg wounds from a colicing horse rolling). Ice packs are used to reduce swelling and prophylactic antibiotics may be given for the skin damage. Scarring may result.

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Penetration/puncture wounds These are wounds in the skin or hoof that may have a small surface area but can extend deep within the tissues. Usually caused by long sharp objects like a nail, thorn or piece of glass and very common in equids. Although they may look unimportant to owners, these wounds can be potentially serious; they are a common cause of tetanus since the deep wound is an ideal environment for anaerobic bacteria. Deeper structures of the foot and synovial structures may also be affected and cellulitis or lymphangitis may result if infection passes into interstitial tissues or the lymphatics. Healing of the skin wound is straightforward but good management of the wound and internal structure is vital.

Incised wounds These include surgical wounds. They are straight, smooth-edged wounds caused by sharp objects such as a knife or a piece of glass. There is minimal tearing or bruising of surrounding tissue but they may be deep and extend to tendons or synovial sheaths.

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Bleeding must be controlled, but healing is usually simple; these types of wound may respond best to suturing, as long as the other requirements for suturing are covered. Scarring is a possibility but rarely limits function.

Lacerated wound More jagged and irregular than an incised wound, caused by uncontrolled tearing of the skin. These are a common wound type, often there are multiple tears and bruising. Bleeding is rare. There may be tissue necrosis. Healing can be difficult to manage, particularly on the lower limbs of equids.

Avulsion A wound where some skin has been lost in the damage. There may also be loss of other tissue underneath. The skin deficit will be an inhibitor of healing. Complicated wound Most wounds in equids are complicated! The injuries may involve other structures, there may be factors that inhibit or delay simple primary closure. The injuries to other organs may be more important than the skin wound, some may even be life threatening. Healing is, therefore, often problematic.

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Burn There are many causes of burns: fire, scalding liquids, friction, chemical/caustic, freezing, sun. Burns are classified according to their extent (% of body surface) and depth of tissue damage (1st, 2nd, 3rd degree). The true extent of the damage may not be obvious at initial presentation.

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3. Wound Healing Wound Healing Process Inflammatory and Debridement phase Blood and fibrin flow into the wound site and form a clot, consisting of mostly fibrin and fibronectin and normal blood cells within a mesh. This clot helps to limit blood loss and provides a platform for the new matrix that will help the migration of cells. This migration of phagocytic cells is vital for the natural debridement of the wound. Foreign matter and bacteria are removed and non-viable tissue is gradually separated from viable areas. Repair phase (proliferation/granulation) Usually starts within the first 12 hours, but it cannot start until blood clots, necrotic tissue debris and infection have been removed. This process of healing requires a good blood supply – angiogenesis is vital for the health of the wound. Healthy, sutured wounds are usually covered in 12-24 hours. Full skin thickness wounds only epithelialise after formation of a granulating bed, requiring a delay of 4-5 days. Granulation tissue is a complex of fibroblasts, vascular endothelial cells and macrophages within a collagen and fibrin matrix. Granulation tissue:

1. Provides a surface for epithelialisation. 2. Is resistant to infection. 3. Is necessary for wound contraction.

The horse is particularly prone to the formation of excess granulation tissue at wound sites on the lower limb. This does not seem to affect ponies or wound sites on the body or head and neck of larger horses unless there are particular reasons for the failure of healing. Maturation phase (Epithelialisation and Contraction) Epithelialisation is a very slow process in which keratinocytes migrate towards the centre of the wound. The process starts within hours of the wound occurring but, on the limbs, continues at a rate of only 1-1.5mm / 10 days. The healing edge of a limb wound may only be visible after 10-14 days. The presence of fibrin clot in the wound will slow the process of epithelialisation, as will the products of chronic inflammation and death of polymorphonuclear leukocytes. The healing epithelium is fragile and thin and poorly adhered to underlying tissue. As the epithelium is restored and underlying fibrous and granulation tissue is remodelled, a scar forms. Tension applied to a wound initiates scar strengthening, although the scar regains only 80% of the original tissue strength after 1 year; the new collagen is a different type which lacks the cross-links of normal collagen. The scar eventually shrinks with decreasing vascularity and cellularity until eventually it is comprised mainly of dense fibrocytes.

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Healing can be achieved in one of three ways: Primary or first intention healing Usually when suturing is used to reunite wound edges and there is no reason for failure of wound healing. Minimal granulation tissue exists and good epithelial migration occurs. In a non infected surgical wound, healing can occur in a short time. Secondary or second intention healing In second intention healing granulation tissue must fill the base of the wound before epithelialisation can be completed. This extends the time needed for healing. Wounds too extensive or contaminated to suture, or those in which primary closure has failed must heal by second intention. Second intention healing relies upon the inflammatory response; the longer the wound takes to heal the greater will be the scar and the possible cosmetic or functional deficits. This may encourage clinicians to attempt to close wounds by primary closure even when this is not indicated by the wound conditions. Second intention healing occurs faster in ponies than horses and faster with body wounds than limb wounds. Delayed primary healing This is a combination of second intention healing in the early stages with a final primary intention healing by suturing after a few days. It is useful in some contaminated wounds in which immediate closure may lead to complications. If closure is delayed for 72-96 hours, only a minimum risk of infection exists. The wound is initially cleaned and debrided but not closed. After a variable period (usually 2-4 days) the wound is surgically debrided and closed by suture as for first intention healing. The advantages of this method are:

1. The wound can be assessed for causes of failure to heal at various stages allowing the best time for closure to be chosen.

2. Acute inflammatory responses and natural debridement can take place before closure without the development of a difficult and prolonged inflammatory process.

There is an inevitable increase in scarring compared to first intention healing. Wound Contraction Wound contraction is the process where intact skin bordering a full thickness skin deficit is drawn in towards the centre over the wound bed in the early stages of repair. It is the major factor in the closure/healing of body trunk or neck wounds in horses. Wound contraction is greater in ponies than in horses and is more pronounced in body wounds than limb wounds. Significant contraction does not usually occur below the carpus or hock.

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Wound contraction usually commences around 6-8 days after a wound occurs and, in small wounds, can be complete in 10-12 days. In large wounds it may take several weeks. Contraction of wounds healing by primary intention is insignificant, but it is most important in wounds allowed to heal by secondary intention. Up to 70% of the skin deficit may be eliminated in this way, the remainder being achieved by epithelialisation.

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4. Principles of wound management

a) First Aid / Emergency Treatment It must be remembered that a wound is not assessed and managed in isolation and the animal may well be suffering from other, more serious, problems. Initial emergency first aid and treatment of problems such as serious haemorrhage is the first priority. Once these have been identified and managed then the animal and the wound can be assessed. b) History As well as the history of the wound, this also includes asking about the history of the animal such as the type of work it does, how it is housed and fed and whether it has any other current or previous health problems. The type of work the animal does is important, especially to understand how the wound might heal, for example if the animal is required for ploughing and the wound is under part of the harnessing, then the chance of it healing quickly are reduced. A thin, weak animal on a poor level of nutrition is also less likely to heal quickly. The owner or keeper should also be asked how long he has owned, or looked after, the animal. The history of the wound involves asking when and how the wound was caused since the answers to these questions may affect the treatment plan and the prognosis. They can also give us an idea of what structures may have been damaged and if there is likely to have been contamination of the wound. Any treatment already carried out by the owner or other people (vets included) should be noted, including existing treatment for other conditions. The owner should be asked if the animal has had any tetanus vaccine and, if so, when was the last one? If this information is not known, it must be assumed that there is no tetanus protection. c) Animal restraint In order to carry out a clinical examination of the animal and to assess the wound, adequate restraint is vital. This is to ensure the safety of the animal, the owner, clinical staff and any other people present. The type of restraint required will depend on the behaviour of the animal, the environment (such as in a SPANA clinic or by the side of a road), the number of people present and the type and position of the wound, but it must be sufficient to allow a thorough examination. Restraint may involve holding the headcollar, picking up a leg, the use of treatment stocks, a lip twitch and/or by medical means. The type of chemical restraint will be decided by the vet and also by their availability but could include an alpha 2 agonist (detomidine, romifidine, xylazine), acepromazine, an opioid drug or a NSAID (non steroidal anti-inflammatory drug). Local anaesthetic drugs may also sometimes be used. Application of local analgesia regionally is preferable to direct application to the wound area as the drug can affect wound healing. General anaesthesia is sometimes required for management of extensive wounds. d) Clinical examination Every wound has an animal attached. As with all injuries or illnesses it is important to carry out a general clinical examination first; including looking at the general body

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condition, age, any other injuries or illness signs and checking TPR (temperature, pulse and respiration). The general condition and health of the animal will also give us information about the wound, for example if the animal is very thin, we know that wounds over bony areas may have caused some bony trauma. A sick animal will also show slower wound healing. e) Initial wound cleaning to remove gross contamination Gloves should be worn on clean, washed hands. Remove large pieces of obvious contamination such as large foreign bodies (if they are not penetrating – take care), pieces of mud, dried scab, blood, sweat from the wound. The wound can then have an initial cleaning with clean water or, preferably, sterile saline. Care must be taken that this washing does not push foreign material further into the wound. Remember to clean the area around the wound which may be contaminated with blood and exudates and may hide further wounds. f) Prevention of further injury and contamination Clip and/or shave the hair around the wound. Shaving with a manual razor (with a disposable blade) works well. This is very important as it allows visualisation of other wounds nearby, keeps the area clear to see how wound healing progresses, and allows more efficient cleaning and dressing. The wound should be protected during clipping or shaving by packing it with a protective gel such as intrasite gel, KY jelly or petroleum jelly or by holding a damp piece of cotton over the wound. g) Wound assessment Hands must be washed and gloved. The finger is the most sensitive piece of equipment to touch, explore and assess a wound, Other senses are important such as the smell of a wound, any sound of crepitus or air flow in a wound, as well as the visual appearance. The wound must be examined carefully and thoroughly. Take your time and remember the anatomy of the area. Consider what structures, such as tendons or blood vessels for example, are close by and may have been affected. The depth of the wound, the damage to visible muscles and bones must be checked, the wound may be a minor problem if the animal has a fractured bone! Sometimes it will be possible to feel a foreign body in the wound. h) Decide on treatment plan Having assessed the wound a treatment plan can be agreed and the initial treatment required can be started. The likely duration of treatment and the probable level of owner ability and cooperation must be considered. The likelihood of getting rest and good nutrition at home is a factor affecting healing and it is important to assess what can be done for the animal in the field. Severe wounds may be better off hospitalised where they can have good nutrition and rest, but this is not always possible. Many of the animals SPANA treats will be straight back to work after initial treatment, we have to try to convince the owners that a few days rest now may prevent a chronic problem that stops the animal working in future. The presence of factors that may affect healing all need to be considered at this stage and these factors reduced or removed wherever possible.

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One of the decisions required on wound treatment is whether to suture the wound or not. Suturing a wound allows it to heal by 1st intention. Skin edges are brought together and there is very little scarring. Most of the wounds SPANA treats will probably be unsuitable for suturing for reasons explained later. i) Wound lavage and debridement One of the most important parts of wound management is lavage (flushing). This assists in the removal of cell debris, foreign material and bacteria from the wound and is ideally carried out with sterile saline solution under moderate pressure. This can be done using a 50ml syringe and an 18 or 19 gauge needle. If sterile saline is not available or is too expensive then a saline solution can be made by using a teaspoon of household salt in 500mls of (preferably boiled and cooled) water. Other antiseptic solutions can be used such as povidone iodine or chlorhexidine. Both must be prepared to the correct dilution. If povidone iodine is to be used the concentration must be no greater than 1%. This allows a balance between the benefits of the povidone iodine (reducing the bacterial contamination of wounds) and the harmful effects (damaging epithelial cells). If the wound is more than 12 hours old, it is likely to be covered by a layer of dead tissue which can delay healing. The thorough lavage may be sufficient, but it may be necessary for the vet to remove this dead tissue (debridement). A scalpel and forceps are best used to accomplish this. Extensive debridement may require general anaesthesia.

j) Infection control The above stages represent preparation of a wound. Time spent in this preparation is never wasted and failure to prepare the wound correctly is a common cause of failed or delayed wound healing. Once prepared the wound may be closed or covered with a dressing to provide the correct environment for healing. A moist wound healing environment is considered ideal and dressings and topical medications should aim to provide this. Wounds with excessive exudate or levels of infection may require different management initially. Up to 6-8 hours after injury, a wound is considered “contaminated”. After this time bacteria have usually become established in the damaged tissues and the wound is classified as “infected”. Infection control involves lavage and debridement, as well as,

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possibly, the use of drains, dressings and systemic antibiotics. Antibiotic use may be indicated to help reduce the rate of bacterial replication, but seldom eliminates infection completely. k) Other treatment Wound repair – suture? A wound should NOT be sutured if:

• It is more than 8 hours old. • There is synovial fluid from a joint or tendon sheath coming from the wound. • There is obvious bone exposed. • There is tendon damage. • The wound is very deep and narrow ( a penetration wound) • There is severe lameness in the leg that is wounded. • There is suspicion of a foreign body.

It is important to consider the provision of pain relief in wounded animals in the longer term, not just whilst examining, assessing and treating the wound. Non steroidal anti-inflammatory (NSAID) drugs such as phenylbutazone, ketoprofen or flunixin are those most commonly available. The importance of tetanus should be remembered (see later), particularly as most animals presented to SPANA are unvaccinated. It is best to administer tetanus antitoxin or tetanus toxoid vaccine (or both) if available when treating an animal with a suspicious wound. l) Duration of treatment Wounds should be regularly reassessed to confirm healing is progressing as expected. Daily wound care is often required; this may be done by the owner who will need careful instruction.

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5. Basic wound management protocol

1. First aid/emergency treatment.

2. History taking.

3. Ensure adequate restraint of animal.

4. Clinical examination of animal.

5. Put on gloves.

6. Remove large foreign bodies from wound.

7. Wash the wound and around with clean water or, preferably, saline.

8. Apply Vaseline or intrasite gel to wound to protect.

9. Shave area around wound with clippers or razor.

10. Assess wound with gloved fingers.

11. Decide on treatment plan.

12. Lavage wound with saline (preferably sterile) under pressure.

13. Debride wound (by vet) if necessary, using scalpel and forceps.

14. Provide appropriate dressing – zinc oxide cream for minor, superficial wounds, bandaged dressing if necessary for others.

15. Ensure sufficient pain relief/anti inflammatory (NSAID) and antibiotic medication

is provided where necessary, plus tetanus anti toxin.

16. Advise owner/user and family on care of the wound and prevention.

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6. Topical medications.

Lavage fluids For lavaging wounds various solutions have been used: Sterile saline This is the ideal lavage solution since it is physiologically compatible with tissue fluid. If the sterile solution is not available or is too expensive, then it can be made with 1 flat teaspoon of salt to 500mls of warm (preferably boiled and then cooled) water.

Water Fresh drinkable water is sufficient to lavage wounds initially but can cause cell swelling with prolonged use. It is best used to remove initial gross contamination of a wound with a following lavage using saline as above. Povidone iodine This is usually supplied as a concentrated solution (often 10%). Strong solutions are damaging to cells and reduce healing. Diluted (0.1 – 1.0 %) solutions actually have greater bactericidal activity than full strength products. 1% solution is, therefore, the maximum strength that should be used for wound cleaning. The scrub product (which contains a soap with the povidone iodine) is not for use as a wound lavage fluid but for use on intact skin and on hands before surgery.

Chlorhexidine This is also usually supplied as a 10% solution, requiring dilution to 0.05 – 1.0% before use on wounds. Stronger solutions have adverse effects on tissues.

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Hydrogen peroxide Hydrogen peroxide was used commonly in the past for wound lavage but is largely now considered unsuitable due to the tissue damage it causes. If nothing else is available it can be used diluted to 5 volumes or less (it is usually supplied as 10 volumes or stronger). Hydrogen peroxide is still used for flushing anaerobic wounds in the sole of the foot for example where there is a likelihood of the presence of anaerobic bacteria that cause tetanus. Other topical products Many products are available in different countries which claim to be for use on wounds. There are powders, sprays, liquids and ointments. If the wound is superficial and not involving major structures, then an antiseptic cream or a wound spray such as one containing chlorhexidine or an antibiotic may be used. This may be necessary in a field situation where the animal may not be seen again and the ability of the owner to clean and dress a wound daily may not be clear. However, it should be understood that this is not ideal. Using lots of different sprays and ointments will not help the wound to heal faster. Sprays in particular, which dry a wound, do not provide the moist wound environment required for good healing. On occasions products containing fly repellents may be required around the wound, these may be either proprietary ones such as ”summer fly cream” or made up of petroleum jelly (300g pot) with 1 teaspoon kerosene mixed in. Ointments containing antibiotics are not generally required; if the wound is severe enough to require antibiotics, these should be given systemically. Similarly ointments or creams containing anti-inflammatories are not helpful in wounds. The products best used on wounds include hydrogels (such as intrasite gel) which provide the correct, moist environment for good wound healing. These are usually, however, expensive and a simple moisture retaining ointment such as Zinc Oxide cream is probably the most useful and available product to use after lavage and debridement of a wound. Vaseline or zinc oxide is also useful to use around a wound to protect the surrounding skin from any discharging exudates. For very deep and infected wounds the use of honey has been found to help reduce infection. However, the honey should be sterile (not often available) and local honeys vary in their antibacterial properties. Sugar has also been used mixed to a paste with povidone iodine and packed into deep wound cavities in the hoof. (100g sugar dissolved in 50ml 1% betadine). This can be of help in the field as an owner can be taught to apply it if necessary.

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7. Dressings and Bandaging Dressings are used to assist the management of wounds and allow the immediate environment to be manipulated to the benefit of wound healing. Historically dressings had a passive role in wound healing, being used simply to conceal and cover wounds. The modern concept of moist wound management means that dressings are now an active component of wound management. The objectives of a dressing are:

1. To enhance and support the healing process. 2. To decrease contamination and further infection at the wound site. 3. To minimize oedema by applying firm, even pressure to the local tissues. 4. To absorb exudates. 5. To maintain a high humidity at the wound and maintain a moist wound

environment. 6. To maintain local temperature and insulate the area against changes in

temperature. 7. To allow gas exchange. 8. To immobilise the wound site (prevent movement) 9. To protect the wound from further trauma. 10. To reduce the risk of fly damage.

There is a great variety of dressings available on the worldwide market these days, most aimed at the human market but with increasing numbers designed specifically for veterinary use. These may include hydrogels such as intrasite mentioned above; hydrocolloids, collagen dressings, hydrophilic foam dressings, alginates and other highly absorbent dressings. There is no single dressing that fulfils all the criteria above, thus there is no single dressing that is idea for all stages of all wounds. The choice of dressing available for SPANA animals may be limited. For simple superficial wounds the use of zinc oxide cream after thorough wound preparation and lavage may be sufficient. More serious wounds are better protected by full dressing (bandaging) Dressing changes The frequency of a dressing change will depend on the type of wound, the local circumstances of the animal and the stage of wound healing. Dressing changes must certainly be made before exudates seeps through to the external layer of a bandage since this can allow the passage of bacteria through to the wound. Changes should also be made before there is any further injury to the site, either from the bandage itself or the exudates which may lead to tissue damage. Some types of dressing can be left on for up to 4-6 days but this should be under conditions where the animal and the dressing can be checked daily.

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Bandage layers Ideally there should be three layers to a bandaged wound dressing: the primary or contact layer, which is held in place by a secondary, absorptive layer and the third layer which holds the dressing in place. Primary (contact) layer This consists of a wound dressing as described above, such as a hydrogel (intrasite), zinc oxide ointment or others. The dressing should not adhere to the wound. Petroleum jelly impregnated gauze is often available in country for human use and is useful as it allows exudates to pass though to the absorptive second layer. Becoming increasingly available are “melolin” like dressings which are non adherent but absorptive and very useful. Gauze is commonly available but should not be used directly on a wound as it will dry it out. It can be used if covered with intrasite or zinc oxide first.

Secondary layer The objective of the secondary layer is to provide support for the primary dressing and provide absorption and padding. Most commonly cotton wool is used; this can easily be moulded around awkward areas and is easy to unroll onto a limb. It is important to use sufficient cotton wool to even out any pressure caused by the outer bandage layer of dressing. Very absorptive dressings such as disposable baby’s nappies can be used on wounds which are producing a lot of exudate or pus. However, they will rapidly dry out non exudative wounds so are generally of use only in the early stages of wound healing. They can be particularly useful for wounds on the back where cotton wool may be harder to secure.

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Third layer This secures and protects the primary and secondary layer. On limb wounds this usually consists of a bandage providing mild compression. Care must be taken if using elasticated bandage which can compromise blood supply, especially if the secondary layer of cotton wool is not sufficient. Adhesive material such as elastoplast or sparadrap can be useful in preventing a dressing slipping down a limb.

On a limb bandaging is easy enough but it is more difficult to apply dressings to the back or other parts of an animal. Dressings, such as baby’s nappies, can be attached by using 4 sutures in the skin at the four corners of the area to be covered. These sutures are put in the skin following the use of local anaesthetic, and often a sedative drug will be needed. The dressing can then be tied in place with the sutures and untied each day to clean the wound and change the dressing.

Alternatively adhesive elastoplast or sparadrap can help with back wounds too, alcohol is required on the skin around the wound (NOT on the wound itself). When the alcohol dries the adhesive bandage should stick to the wound. Application of a dressing Until the wound has granulated, any dressing applied has two main functions: to absorb exudates and to prevent further trauma, contamination and infection. In addition to the materials used, consideration should be given to how tightly the bandage should be applied. It should apply minimal pressure to avoid further compromise to the blood supply at the wound site. Once granulation tissue has filled any tissue deficit to the skin level, a firm pressure bandage will help to prevent excess granulation tissue. Care must always be taken to avoid causing skin necrosis. Any indication that the dressing is not

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comfortable for the animal must be regarded as important and the bandage checked immediately. The most vulnerable sites are over the accessory carpal bone in the forelimb and over the Achilles tendon 5-10 cm above the point of the hock. Dressings that completely enclose the hock or the knee(carpus) significantly restrict movement and are resented by the animal who may disturb the dressing. Adding extra padding over the accessory carpal bone and to both sides of the Achilles tendon will help to distribute pressure of the dressing. The point of the hock may be left uncovered by the dressing.

With back wounds and wounds at areas of harness contact, ideally the animal will be rested during the healing process. If this is impossible for the owner to comply with, then suitable padding such as doughnut bandages should be provided to keep the wound itself away from contact with the harness or saddle. These doughnut bandages must be sewn under the saddle in the correct spot and checked regularly that they are not becoming a source of pressure and contamination themselves, especially if the wound is exudative.

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8. What not to use on wounds. Strong antiseptic solutions such as concentrated iodine solutions – these damage epithelial cells and slow healing. The possible slight benefit of killing bacteria is generally outweighed by the negative effect on epithelial cells. Low concentrations of povidone iodine (0.1%) have been shown to have greater bacteriocidal activity than higher concentrations. Battery acid – only negative effects on body tissues. Mud – will contaminate wounds with soil bacteria, including tetanus. Engine oil – contains carcinogens and tissue damaging chemicals which can also harm internal organs such as the liver if absorbed into the body. Caustic chemicals such as copper sulphate, potassium permanganate or silver nitrate – damage tissue repair mechanisms. Wound powders – mostly of no proven efficacy and will dessicate a wound. Corticosteroid creams – suppress wound contraction and the acute inflammatory stage which is vital for good repair. (May, however, be useful in later stages to control chronic inflammation)

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9. Factors affecting healing. Early recognition of factors that delay healing will allow their correction or management to reduce their effect. Delayed healing results in the development of chronic inflammation and also, possibly, the production of excess granulation tissue. The factors that delay healing are listed below: Infection/infestation Infection control with thorough wound cleaning and preparation as previously described is most important to prevent bacterial or fungal colonisation of a wound. Mixed infections are common. Staphylococcus aureus infection can resemble granulation tissue or sarcoid. Parasitic infestation with Habronema sp or with the larvae of certain flies (myiasis) will also retard healing (although, under controlled conditions, the sterilised larvae of Lucilia sericata have been used for a beneficial debriding effect in wounds). Movement Movement at the site or in the attached tissues delays healing. Hence wounds over joints or tendons must be managed particularly carefully. Bandaging (with Robert Jones dressings) or even splinting or casting is sometimes used to prevent movement in the early stages of a difficult wound. Foreign body The presence of foreign bodies in the wound is one of the most common reasons for non healing. These may be sand or grit, metal, wood or plant matter from the cause of the wound or necrotic tissue (see below). Care must be taken during clipping or shaving a wound that hair is not allowed to pass into the wound and become a foreign body. Sutures are also foreign bodies but modern materials such as monofilament and absorbable synthetic materials used are less likely to affect healing. Necrotic tissue Devitalised tissue of any type (skin, connective tissue, muscle, tendon or bone) will delay healing. Tendon and bone may take some time to show obvious necrosis, so it may be several months before the necrotic tissue is obvious. Careful debridement of all non-viable tissues at the initial stages of wound management is important. It is often wise to allow time for necrotic tissue to become obvious before wounds are closed (delayed primary healing). Altered local pH Some bacteria will produce acidic conditions in the local environment and others will produce an alkaline one. Ideal circumstances for healing should be a neutral pH approximately, or very slightly alkaline. Poor blood supply Blood supply to the region may be damaged by:

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• Major vessel damage (haemorrhage) which can even lead to gangrene. • Bruising, oedema or thrombosis. • Damage to the microcirculation from ischaemia (including vasoconstriction

caused by adrenaline in local anaesthesic agents) • Anaemia – heavy blood loss and conditions causing severe anaemia – can

significantly delay healing. Some areas of the horse’s skin such as the dorsal hock region are thought to have a naturally poorer blood supply than other areas. Poor Oxygen Supply Adequate oxygenation is important for normal healing; a poor supply slows healing and encourages the development of chronic inflammation. Severe anaemia will also cause low oxygen tension; the cause of the anaemia must be addressed. Anaerobic conditions in a wound can allow the development of some of the most serious clostridial infections such as tetanus. Modern dressings are usually gas permeable and allow oxygen to reach a wound. Poor health or nutritional status Wounds on debilitated and/or old horses heal more slowly than on healthy young ones. Animals with Cushings disease (hyperadrenocorticism / PPID Pituitary pars intermedia dysfunction) commonly have wounds that heal poorly because of high levels of circulating cortisone. A horse with significant anaemia or hypoproteinaemia as a result of a wound can lose weight and the wound may fail to heal. Hypoalbuminaemia significantly retards healing and encourages chronic inflammation. Vitamins A and C (and K and E ?) deficiency can also retard healing. These factors emphasise the need to carry out a thorough clinical examination of all cases. Local factors Wounds with a pouch of skin, which cannot drain effectively, and excess dead space fail to heal. The accumulated tissue fluid is an ideal medium for bacterial replication. If a wound appears to be irritating to the animal and causes self trauma think also of equine rabies. Wounds with parasitic infestations may also be irritating. A low environmental temperature will slow healing as will dehydration (dessication) of a wound. Iatrogenic factors Incision, swabbing, haemostasis by forceps, ligatures and sutures all damage tissue to some extent. Adverse reactions to sutures can be minimised by using:

• The finest gauge material sufficient to appose the tissue. • Atraumatic needles. • An appropriate suture pattern. (no gaps unless purposely for drainage) • The least amount of suture material necessary. • Sutures must not be too tight.

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Excessive pressure from dressings can compromise blood supply and surface oxygen levels. Pressure is sometimes used to control or prevent excess granulation tissue but this must be done very carefully. The most common iatrogenic factors encountered are the uses of inappropriate chemicals on wounds; these include:

• Strong antiseptic solutions (such as povidone iodine greater than 1% concentration)

• Caustic chemicals such as silver nitrate, potassium permanganate or copper sulphate which damage tissue repair mechanisms.

• Various “wound powders” available in the market but no longer recommended. • Substances used by owners such as engine oil or battery acid. • Topical corticosteroids. Corticosteroids suppress the acute inflammatory stage

and wound contraction, both of which are vital for good wound healing. Systemic corticosteroid treatment (oral or by injection) may also encourage infection by suppressing macrophage and neutrophil activity within the wound. (corticosteroids can be useful in managing chronic inflammation such as excess granulation tissue but must be used carefully.

Genetic factors Individual animals vary in their wound healing properties. Larger horses heal less well than ponies, especially in the lower limbs. Cell transformation This is usually in the form of sarcoid (tumour) transformation which occurs at wound sites. Healing will be inhibited unless all tumour cells are removed. Sarcoid lesions at other places on the body or on “contact” horses, predispose to tumour transformation at the wound site. Flies may be involved in sarcoid transformation. Wounds on equids with sarcoids at other sites should be treated particularly carefully, no matter how small or insignificant the wound appears to be.

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10. Other complications and wound management techniques. Minimising problems with healing

• Early intervention • Application of sound surgical principles • Use of appropriate debridement techniques • Use of suitably placed surgical drains • Minimising dead space • Reducing and controlling infection • Eliminating and preventing contamination • Use of physiologically sound wound lavage mechanisms

Management of granulation tissue Granulation tissue forms faster in horses than in ponies or donkeys and this can result in the apparent expansion of the wound site. Many accidental wounds produce granulation tissue, in fact it is essential in most cases where repair is reliant on second intention or delayed primary union healing. Excess granulation tissue protruding from healing wounds is a common problem in horses, especially on limbs. When excess granulation tissue develops on wounds on the head or body trunk there is usually an identifiable reason such as a foreign body or necrotic tissue. The rate of production of granulation tissue can be partially controlled by limiting the extent of the inflammatory response by infection control, removal of foreign bodies and careful management of the early stages of the wound. Movement of tissue around wounds also makes excess granulation tissue more likely, another reason why rest is so important. Local application of corticosteroids can be helpful, as can application of a pressure bandage to reduce the rate of granulation tissue production. Bandaging and supporting a wound will also help. Some cases of excess granulation tissue may be affected by sarcoid or by bacterial involvement (such as a staphylococcal pyogranuloma). These can be difficult to diagnose clinically but must be considered in cases which fail to resolve with treatment and management. Sarcoid and staphylococcal pyogranulomas are difficult to manage in the field. If the likely cause of the excess granulation tissue can be identified and managed, resolution should be possible. If a cause can not be found, then the idiopathic excess granulation tissue is best removed surgically: There are no nerve endings in this tissue so general anaesthesia is not generally required. The bed of granulation tissue should be removed to 0.5 cm below skin level, this excision

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(with a scalpel blade) may be necessary on several occasions before epithelium completely covers the wound. Pressure bandaging can be used to control haemorrhage. There is no justification for using caustic substances such as copper sulphate; these are non selective in their action and will destroy the delicate advancing epithelial margin. Management of exudate Excessive wound exudate is unusual in horses. Extensive skin loss, burns or large bleeding/granulomatous wound sites usually have the most exudate. Chronically infected wounds and wounds complicated by sarcoid may also produce excess exudate. Wounds involving synovial structures or secretory glands or ducts will also produce fluid. Exudate can be:

1. Haemorrhage (capillary seeping or more obvious venous or arterial haemorrhage). 2. Serum/plasma exudates. 3. Inflammatory fluids, often infected.

The exudates should be controlled by appropriate wound management through:

1. The use of pressure bandages. 2. Infection control. 3. Placement of a suitable drain. 4. Surgical removal of infected or excess granulation tissue. 5. (Treatment/management of sarcoid. 6. Restoration of synovial integrity or duct continuity. 7. Obliteration of secretory glands.)

Use of surgical drains Excess fluids and exudates can be harmful to wound healing; they keep healing tissues apart and harbour infection. Some wounds allow natural, passive drainage of fluids by gravity; this can be encouraged by partial closure of a wound or by placing a surgical incision to allow drainage (usually at the most dependent part of a wound). Drains are used to remove accumulated fluids from a closed or partially closed wound. The placement of a drain is critical; it must not simply be laid through the wound under the skin. In this way it will not function properly, may act as a foreign body and reduce healing. Drains must be placed deep in the wound and should exit some distance from the edge of the wound. Bandage drains (seton) A length of cotton bandage is passed into the cavity of a wound and allowed to drain. The bandage can be moved back and forwards to encourage drainage and delay healing until the wound is ready to close. Care must be taken since the drain itself may allow infection to gain access to the wound site or bits of cotton from the bandage may be come detached and act as foreign bodies.

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Penrose drains Made of latex and useful if available. They are simple to use and remain effective until removed. Fluid drains by surface tension of the latex – cutting holes in the rubber does not help. Skin Grafting Grafting is an effective method of managing granulation tissue but is not usually suitable for managing cases where there are identifiable reasons for the non-healing of the wound. If there is chronic infection, foreign bodies, sarcoid cells, excessive movement, necrotic tissue or poor blood supply it is unlikely to heal with grafts. Grafting should not be attempted until the wound is in a suitably healthy state, but it is sometimes possible to divide a wound into the healthy and unhealthy areas. The healthy areas can be grafted while the unhealthy managed in other ways to restore a healthy bed of granulation tissue free of infection. Skin grafts can be considered where there is a full thickness skin deficit, epithelialization is not active or is retarded, and where wound contraction is not occurring. Skin grafting can improve wound healing, with fewer functional problems and a shorten recuperation time. There are several types and methods of grafting, the simplest and most applicable to many SPANA cases are Pinch Grafts. Pinch grafting This is a simple and practical method requiring no special instrumentation and can often be done in the standing animal (possibly under sedation), with the use of local anaesthesia at the donor site.

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The common donor site is the side of the neck where an inverted L block of local anaesthesia is used to desensitise the site. The site chose must of course be healthy and is prepared as if for surgery.

Discs of 3-4 mm of skin are elevated with the point of a half curved cutting needle held in needle holders. These discs are excised with a number 11 scalpel blade and placed in a clean dish or on a piece of gauze soaked in sterile saline. It is best to start at the bottom of the donor site to avoid bleeding obscuring the site. Around 15 discs can be collected at one time. The recipient site should be prepared by gentle cleaning with sterile saline only. The pinch grafts are then implanted in the granulation tissue, 1cm apart in a downward direction at an angle of 45º using fine, pointed, curved, plain tissue forceps. Again, it is best to start at the bottom so that bleeding does not obscure the site. The recipient site does not require the use of local anaesthesia. The wound is then covered with a dressing such as a paraffin gauze dressing or melolin. Movement will cause some of the grafts to be dislodged which will be noticed when the dressing is changed in 3-4 days. Loss of more than 10% of the grafts is usually due to poor technique. Successful grafts have a good effect in controlling granulation tissue and can be recognized by blanching (whitening) of the granulation tissue bed (between 7-21 days) as neovascularisation is inhibited. More active epithelialisation is also seen at the periphery of the wound and obvious wound contraction is evident around 21-28 days after grafting. Islands of graft derived epithelium are visible around 21-35 days and tufts of hair may be visible around 42-56 days.

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The success of grafting depends on: • The preoperative care and management of the donor and recipient sites. • The state of the recipient site – healthy, pink granulation tissue. • The reduction of movement after the graft by bandaging.

Wound related problems Tetanus Equids are frequently afflicted by wounds and injuries, they are also, unfortunately, very sensitive to the toxin produced by the anaerobic bacteria Clostridium tetani. Tetanus, therefore, must be considered as a possible sequel to any wounds on a horse, donkey or mule. This is all the more important given that the majority of the animals seen by SPANA will not be vaccinated against tetanus. Rabies Rabies is a zoonosis which is fatal and the safety of SPANA personnel and the general public must be a priority. Great care must be taken with any equine animal suspected of being rabid or of being bitten by a rabid animal. The owner of the animal may be aware that the wound was caused by a dog bite but any acute traumatic wound of unknown origin that could be a bite must be treated with suspicion. Frequently animals are presented with a healed, old wound, which may appear to be irritating the animal, causing persistent licking or self mutilation at the site. Equine animals with clinical rabies generally show neurological signs with depression, hind limb ataxia leading to complete paralysis, coma and death. Excess salivation and an inability to swallow can also be signs causing owners to suspect a pharyngeal or oesophageal foreign body; colic signs may also be present. Occasionally the “furious“ form may be present with the animal exhibiting aggression. In most countries Rabies is a notifiable disease and the authorities should be contacted with any suspect rabies case. The animal should be isolated and a strict management protocol should be in place which every member of staff understands fully and implements. ALL SPANA staff must be vaccinated against rabies and keep the vaccinations up to date. Special wounds Synovial structures Wounds resulting in penetration of any synovial structure can lead to serious infection and major lameness. The skin injury may appear small and trivial but extend deep into the synovial structures; it is important to understand the anatomy of the region underlying a wound. Synovial fluid leakage may be apparent; this is clear, yellow and viscous. Immediate and thorough treatment of any wounds involving synovial structures is vital if an adequate return to function is possible, this treatment will involve careful exploration

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by the vet, lavage and flushing with sterile saline, protection of the wound and continued antibiotic and anti inflammatory therapy. Hospitalisation and rest is important. Damage to tendons Wounds over tendon sheaths must be explored carefully to identify any possible tendon damage, as well as the damage to the synovial structure. Close examination of the posture of the foot and fetlock when the leg bears weight will also help to identify tendon disruption. Exposed bone Exposure of bone occurs most often on the distal limb and the face. When there are pieces of non viable bone, with loss of periosteum, the blood supply is disrupted and sequestrum formation occurs. This may take several weeks to become apparent after the wound occurs and is a common reason for the non healing of a wound. Often an Xray is required to confirm the diagnosis. Removal of the piece of sequestered bone is then required for good healing. Fresh wounds with exposed bone should be treated carefully with a standard protocol and the wound allowed to granulate with good infection control. The owner should be told that the likelihood is that the wound will heal slowly and will most likely require surgery to remove sequestered bone after several weeks. Eyelid injuries Eyelid injuries are quite common in equids. Upper eyelid wounds are more important than lower ones in that they perform 76% of the blink function. Therefore scarring and deformity of the upper lid can have long term harmful effects on eye function. Injuries to the medial aspects of the lids can involve the lacrimal punctae and/or the lacrimal duct. Eyelid injuries can be difficult to examine, skin flaps should not be cut off and good repair will require general anaesthesia.

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11. Extension messages to owners

Treating existing wounds when presented is one part of SPANA’s work. Staff must also be prepared and active in talking to owners about the management and continued nursing of wounded animals, but also about prevention of wounds in future. It is important that SPANA staff feel confident to advise owners on the following: Prevention of wounds

• Animal health in general • Harness maintenance • Cart maintenance • Work load and nutrition

Wound management

• Owner 1st aid • The importance of obtaining professional help quickly • What NOT to do and why

Wound healing

• Rest, nutrition, clean environment • Regular cleaning • Harness repair/change • Beating?

We need to advise owners how to protect wounds, especially if they are caused by poor harnessing or saddles. We must advise them on proper saddlery and harnessing, and we can consider the use of padding around wounds to protect them if they really must work. SPANA clinics should have access to humane hobbles and bits, doughnut bandages, noseband covers and other bits of harness protection, and staff must be able to fit them and teach owners how to use them.

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12. References and Further Reading. Coombs S., 2002. The SPANA guide to Animal Care. SPANA. Knottenbelt D.C., 2003. Handbook of Equine Wound Management. Saunders. Knottenbelt D.C., 2006. Equine Formulary. Saunders, Elsevier. Websites – suturing, wounds, general information: http://www.horseandhound.co.uk/horsecare/1370/82206.html http://www.vwms.org/ http://www.vwha.net/index.html http://www.newc.co.uk/advice/documents/Mills.pdf?PHPSESSID=d81ed5cc437c005b5299ccd2a63ed6c8 http://www.iviers.com/mielet.htm http://cal.vet.upenn.edu/surgery/